Did a Comet, Asteroid or a Giant Volcano Kill Off the Dinosaurs?

As you stand under the towering T-Rex fossil at the Natural History Museum or marvel at the sheer size of the diplodocus, it does make you wonder, where are they now? Well the jury keeps swaying its opinion as to what happened and just what caused the velociraptor to stop running. The latest in an array of possible causes of the 'Death of the Dinosaurs', is the possibility that it was a comet that was responsible for the dinosaurs demise.

A high velocity comet hitting the Earth around 66 million years ago... just after lunch!. Well what happened to the planet, and how can we be sure what caused it.

It's known as the 'End-Cretaceous mass extinction' and it was an important event in the history of our planet (particularly if you were a big dinosaur!!). Some 16% of all marine families, 47% of all genera, an estimated 71-81% of all species became extinct when something big happened to the planet. At the same time in the Earth's history, a giant volcanic event happened that erupted thousands of cubic kilometres of lavas, and with the lavas came a lot of toxic gasses. This event has also been linked with the End-Cretaceous mass extinction.

An impact from outer space is implicated in shuffling the big beasts off this mortal coil, due to a rather large impact crater in Mexico, known as the Chicxulub impact crater (http://neo.jpl.nasa.gov/images/yucatan.html), and also a spike in iridium (a rare metal similar to platinum and an element found in abundance in space) in rocks around the world at this time. This points to a large asteroid impact to hit the Earth.

With the recent Russian meteorite strike, this is very much a reality in our minds and in the long history of the Earth, including around 66 million years ago.

This recent contribution to the debate of how the dinosaurs died is fuelled by the iridium anomaly, or lack of it, compared to the predicted size of a slow moving asteroid strike. It suggests that in order to create the impact crater and the measured iridium layer around the world, you need a fast comet to impact. This may be true, as is the fact that large volumes of lava also erupted over the planet, and the consequences from one or both of these events was enough to cause a major change in our planets climate, and indeed it's evolutionary direction.

The debate will continue, with 'eruptionists' on one side and 'impactors' on the other, and the in-fight between 'asteroid admirers' and 'comet convertors' will probably go on long after the pub closes. As the night draws closer though, I would like to throw into the hat a rather interesting take on how the dinosaurs, well at least T-Rex, died out due to his hunting technique... enjoy!